Process for hydrocracking nitrogen-containing feedstocks

ABSTRACT

The process comprises introducing a first portion of a feedstock containing at least 20 parts per million of nitrogen into a feedpreparation zone to reduce the nitrogen and sulfur contents thereof; treating the effluent from the feed-preparation zone to separate a hydrogen-containing light gas and a heavy bottoms fraction from the effluent; introducing the treated effluent into a hydrocracking zone; and introducing a second portion of the feedstock containing at least 20 parts per million of nitrogen into the hydrocracking zone at a plurality of points spaced along the length of the hydrocracking zone to provide an increasing amount of nitrogen along the length of the hydrocracking zone in the direction of flow through the hydrocracking zone. The nitrogen-containing feedstock is introduced into the hydrocracking zone at a plurality of points along its length to control effectively the rate of reaction in the hydrocracking zone. The heat of the controlled hydrocracking reaction is used effectively to reduce external heat supplied to the hydrocarbons prior to their entry into the hydrocracking zone.

United States Patent Hengstebeck [45] A 1'. 18 W72 [54] PROCESS FOR HYDROCRACKING NITROGEN-CONTAINING Primary Examiner-Delbert E. Gantz FEEDSTOCKS Assistant ExaminerG. J. Crasanakis Attorney-Arthur G. Gilkes, William T. McClain and James L. [72] Inventor: Robert J. Hengstebeck, Valparaiso, Ind. Wilson 7 [73] Assignee: Standard Oil Company, Chicago, Ill. [57] ABSTRACT [22] Med: 1970 The process comprises introducing a first portion of a feed- [21] A N 544 stock containing at least 20 parts per million of nitrogen into a feed-preparation zone to reduce the nitrogen and sulfur con- Related U.S. Application Data tents thereof; treating the effluent from the feed-preparation e zone to separate a hydrogen-containing light gas and a heavy [631 g gg g gglggggf of bottoms fraction from the effluent; introducing the treated effluent into a hydrocracking zone; and introducing a second [52] CL 208/89 208/111 portion of the feedstock containing at least 20 parts per mil- [51] Int clog 23/00 lion of nitrogen into the hydrocracking zone at a plurality of [581 newofs;.a.ti;::::......... .IIII56)""'2"1'2 108 109 eeiee eeeeee eleee ehe leeeeh ef ehe hyeeeeeeeleee ee 20871 1 provide an increasing amount of nitrogen along the length of the hydrocracking zone in the direction of flow through the hydrocracking zone. The nitrogen-containing feedstock is in- [56] References cued troduced into the hydrocracking zone at a plurality of points UNITED STATES PATENTS along its length to control effectively the rate of reaction in the hydrocracking zone. The heat of the controlled hydrocracking gengsttebleck reaction is used effectively to reduce external heat supplied to e ass a the h drocarbons rior to thei ent 'nt the h d k' sass; 24:22: e e ----2--.;8-i:4 .2 P y 1 e 3,008,895 1 1/1961 Hansford et al. ..208/89 Claims, 2 Drawing Figures M k -u i r E )J I v flyzr ageel 42 44 45 Reaction Zone 2 H d A" Z 33 m me In one i ,3 y c E a Feed i a4 Feed -Preparaf/0n Zone FLASH l d 2351) 25" FRAG T/O/VA T0)? 250% 39 38 PATENTEDAPR 18 I972 SHEET 10F 2 l/V VEN TOR. Robert J. Hengstebeck BY%- .'W3H

ATTORNEY PROCESS FOR HYDROCRACKING NITROGEN- CONTAINING FEEDSTOCKS CROSS-REFERENCE TO RELATED APPLICATION This is a continuation-in-part application of application Ser. No. 546,447, filed on Apr. 29, 1966, and now abandoned.

BACKGROUND OF THE INVENTION This invention relates to the catalytic conversion of petroleum hydrocarbon feedstocks. More particularly, it relates to an improved processing scheme for the hydrocracking of relatively high-boiling petroleum hydrocarbon feedstocks containing nitrogen compounds to produce lower boiling hydrocarbons which boil predominantly in the gasoline boiling range.

Hydrocracking is a general term which is applied to petroleum refining process wherein hydrocarbon feedstocks which have relatively high molecular weights are converted to lowermolecular-weight hydro-carbons at elevated temperature and pressure in the presence of a hydrocracking catalyst and a hydrogen-containing gas. Hydrogen is consumed in the conversion of organic nitrogen and sulfur to ammonia and hydrogen sulfide, respectively, in the splitting of high-molecular weight compounds into lower-molecular-weight compounds, and in the saturation of olefins and other unsaturated compounds. In hydrocracking processes, hydrocarbon feedstocks, such as gas oils that boil in the range of about 350 F. to, about l,000 F., typically, catalytic cycle oils boiling between 350 F. and 850 F., are converted to lower-molecular-weight products, such as gasoline-boiling-range products and light distillates. Typical hydrocarbon feedstocks contain nitrogen compounds in amounts in excess of 20 parts per million. Nitrogen compounds in hydrocarbon feedstocks tend to reduce the activity of the catalyst used in the refining process. Such reduction in catalytic activity results in inefficient operation and poor product distribution and yields. As the nitrogen content increases, higher reaction temperatures are required to maintain a given conversion level. Generally, the nitrogen content of a hydrocarbon feedstock can be reduced by processing that feedstock in a hydrofining operation. In such instance, the nitrogen compounds are converted into ammonia and the resultant ammonia and other gaseous constituents are separated from the liquid of the hydrocarbon feedstock prior to its introduction into the hydrocracking process reaction zone.

Nitrogen compounds have a deleterious effect upon hydrocracking catalysts. This poisoning effect may result from the adsorption of nitrogen compounds on the active acidic sites of the catalyst. In such a case, the cracking activity of the catalyst is suppressed. One way of minimizing this selective poisoning is to operate the hydrocracking process at high temperatures. When this is done, however, much light gases and coke are produced and the rate of catalyst deactivation is accelerated. This selective poisoning can be harnessed to a particular process to provide benefits for that process. For example, R. H. Dudley et al., in US. Pat. No. 2,935,464, have introduced into a reforming process small amounts of ammonia or other nitrogencontaining compounds, such as alkyl or aryl amines, to effectively suppress the excessive cracking or hydrocracking that occurs when certain sulfur-containing feedstocks are charged to the process. The nitrogen-cntain ing compounds may be added to the recycle gas or the hydrocarbon feedstock in amounts which fall within the range of aboutl to about 20 parts per million, preferably 2 to 5 parts per million, based upon the feedstock. Also, Haensel et al., in U.S. Pat. No. 2,906,699, have introduced into a process for the reforming of a sulfur-containing naphtha, halogen-free, basic-nitrogen-containing hydrocracking suppressors and have regulated the amount of these suppressors added thereto to control the hydrocracking. From 2 to 200 parts per million of the additive may be necessary, depending upon the amount of sulfur in the feed. Ciapetta et al., in US. Pat. No. 3,023,159, have either added nitrogenous compounds to or removed them from a hydrocarbon fraction, or both, before hydrocracking to change the nitrogen content of that particular fraction in order to control the hydrocracking conversion of that fraction to lower boiling products. Arey, in US. Pat. No. 3,213,013, has regulated a hydrocracking process employing a catalyst comprising crystalline alumino-silicate zeolites having incorporated therein a platinum-group metal and small amounts of Na i) by adding a catalyst poison, which is normally a nitrogenous base material, preferably ammonia. Arey initially conducts the hydrocracking reaction at a desired specific temperature in a relatively high concentration of the catalyst poison which is sufficient to temporarily suppress the initial activity of the zeolitic-based catalyst so as to prevent excessive cracking to undersired products and thereafter reduces the amount of nitrogenous base material as the run progresses in order to maintain a constant conversion at the relatively constant high-temperature level and feed rate.

SUMMARY OF THE INVENTION Broadly, inaceordance with the present invention, there is provided a hydrocracking process which comprises: treating in a feed-preparation zone a first portion of feedstock containing at least 20 parts per million of nitrogen to reduce the amount of nitrogen in the feedstock; supplying external heat to at least part of the treated feedstock; introducing the heated treated feedstock into a hydrocracking zoneto contact a hydrocracking catalyst under hydrocracking conditions; introducing a second portion of feedstock containing at least 20 parts per million of nitrogen into the hydrocracking zone at a plurality of points spaced along the length of said hydrocracking zone to provide an increasing amount of nitrogen along the length of the hydrocracking zone in the direction of flow through the hydrocracking zone, said increasing amount of nitrogen being effective to control the rate of reaction in the hydrocracking zone so that the heat of reaction may be used effectively to reduce external heat supplied to the hydrocarbons prior to their entry into the hydrocracking zone, without appreciably deactivating the hydrocracking catalyst; and recovering the lower-boiling hydrocarbons as usable petroleum products.

BRIEF DESCRIPTION OF THE DRAWINGS Two drawings accompany this application. The operation of the improved process of the present invention and the advantages thereof will be understood from the description of the invention which follows when read in conjunction with the accompanying drawings.

FIG. 1 is a highly simplified schematic flow diagram of a preferred embodiment of the process of the present invention.

FIG. 2 is a highly simplified schematic flow'diagram of a hydrocracking process employing techniques well known to those skilled in the art, that is, a hydrocracking process of conventional design.

Since these figures represent simplified flow diagrams, they do not include various pieces of auxiliary equipment, such as heat exchangers, condensers, pumps, and compressors, which, of course, would be necessary for complete processing schemes and which would be known and used by those skilled in the art.

DESCRIPTION AND PREFERRED EMBODIMENT Not one of the above-discussed patents considers a process which provides an increasing amount of nitrogen along the length of a hydrocracking zone in the direction of flow through the hydrocracking zone, which increasing amount of nitrogen is effective to control the rate of hydrocracking reaction so that the heat of reaction may be used effectively to reduce the amount of external heat supplied to-the hydrocarbons prior to their entry into the hydrocracking zone. However, my improved hydrocracking process does provide an increasing amount of nitrogen along the length of the hydrocracking zone and this increasing amount of nitrogen is such as to control effectively the rate of the hydrocracking reaction so that the heat of reaction may be used to supply a substantial amount of heat to the hydrocarbons. In view of this, the hydrocarbons do not have to be heated to as high a temperature prior to their introduction into the hydrocracking zone. As a consequence, the amount of heat-exchange surface needed to heat and cool the hydrocarbons is substantially reduced.

it is to be noted that the first portion of feedstock containing at least 20 parts per million of nitrogen need not be the same nor have been derived from the same source as the second portion of feedstock. Of course, they can be the same or derived from the same source.

In the normal operation of a hydrocracking unit today, the temperature in the hydrocracking zone is held within a rather narrow range; for example, the temperature variation across the reaction system may be no greater than 25 F. The rate of reaction is controlled to permit the temperature to rise a certain number of degrees and then the reactants are cooled to a lower temperature by means of inter-bed cooling.

In my improved hydrocracking process, inter-bed cooling need not be employed. The temperature throughout the entire length of the hydrocracking zone is allowed to rise so that there is a large temperature gradient across the entire length of the hydrocracking zone. Such a temperature rise may exceed 100 F. Hydrocarbons containing nitrogen are added at selected points along the length of the hydrocracking zone. As the hydrocarbon stream passes through the hydrocracking zone, heat is liberated by the reaction and the temperature rises. The introduction of nitrogen at a plurality of points prevents the rate of reaction increasing to such an extent that rapid catalyst deactivation occurs at the higher resulting temperatures.

Two types of catalyst deactivation occur in the hydrocracking system. There is a slow deactivation which is caused by a slow accumulation of coke or by slow changes in the structure of the catalyst. There is also a rapid deactivation which results from the rapid deposition of coke at increased reaction rates and temperatures. There is not much that one can do to control the slow deactivation of the hydrocracking catalyst; however, one can prevent the rapid deactivation of the hydrocracking catalyst. Regulation of the rate of reaction at increased temperatures may be accomplished by adding nitrogen to the hydrocracking system.

A prime purpose of my present invention is to reduce the amount of external heat that need be supplied to the hydrocracking zone. Such a reduction of external heat that is to be supplied to the hydrocarbons prior to their entry into the hydrocracking zone will result in less fuel requirements and less heat-exchange surface to heat and cool the hydrocarbons.

A considerable investment in heat-exchange equipment and flashing equipment for suitably handling the effluent from the feed-preparation zone prior to hydrocracking would be required in a conventional two-stage hydrocracking process. It is well known that heat-exchange equipment accounts for a large share of the total cost in the construction of a hydrocracking system. For example, the cost of heat exchangers and furnaces would account for almost 40 percent of the estimated materials cost for a conventional hydrocracker that would process 15,000 barrels per stream day of light catalytic cycle oil. My improved hydrocracking process permits lower investment in equipment and, consequently, a more economical operation.

In my improved process, the amount of external heat is reduced by the substitution therefor of the heat resulting from the cracking zone. Nitrogen-containing hydrocarbons are added at selected points along the hydrocracking zone so that the nitrogen content of the hydrocarbons in the hydrocracking zone increases in the direction of flow through the hydrocracking zone. The increasing amount of nitrogen must be sufficient to control the rate of reaction at the increased temperatures along the length of the hydrocracking zone to prevent appreciable deactivation of the catalyst.

It is believed that the following may describe essentially what occurs when the catalyst is contacted with the hydrocarbon feedstock containing nitrogen compounds. However, it must be understood that this proposed theory is presented only to facilitate the understanding of my invention and is not intended to limit what actually occurs in the reactor.

Generally, as temperature is increased, the rate of reaction increases. As the rate of the hydrocracking reaction increases more hydrogen is required, with a result that the hydrogen pressure at the catalyst surface is reduced. But the hydrogen pressure should be maintained at a level above which the deactivation of the catalyst occurs at an acceptable rate. If the hydrogen pressure should fall below this level, catalyst deactivation rapidly accelerates. The use of a selective poison to impede the hydrocracking reaction at increased temperatures can prevent the hydrocracking reaction from using that amount of hydrogen which will lower the hydrogen pressure at the catalyst surface to a level where catalyst deactivation rapidly accelerates. in my hydrocracking process, the tem perature is permitted to increase along the length of the hydrocracking zone to such an extent that the temperature gradient from the top to the bottom stream; introducing into the hydrocracking zone the heated mixed hydrogen-hydrocarbon stream; hydrocracking in the hydrocracking zone the heated mixed hydrogen-hydrocarbon stream in the presence of a hydrocracking catalyst under hydrocracking conditions; introducing a second portion of feedstock containing at least 20 parts per million of nitrogen into the hydrocracking zone at a plurality of points spaced along the length of said hydrocracking zone to provide an increasing amount of nitrogen along the length of said hydrocracking zone in the direction of flow through the hydrocracking zone, which increasing amount of nitrogen is effective to control the rate of reaction in the hydrocracking zone so that the heat of the hydrocracking reaction may be used efiectively to reduce external heat supplied to the hydrocarbons prior to their entry into the hydrocracking zone, without appreciably deactivating the hydrocracking catalyst; mixing the effluent from the hydrocracking zone with said first portion of feedstock prior to introducing said first portion of feedstock into the feedpreparation zone; and recovering the light overhead products as usable hydrocarbon products.

Generally, low-temperature hydrocracking processes for maximizing gasoline-boiling-range products employ two processing stages, although recently single-stage processes have been devised. In a typical two-stage process, the feedstock is hydrotreated in the first stage to remove the nitrogen and sulfur that are typically found in the usual refinery feedstocks. In the second stage, the pretreated hydrocarbon stream is converted to lower-boiling products. Consequently, the first stage is a feed-preparation stage and the second stage is a hydrocracking stage. In such a two-stage process, essentially no hydrocracking would occur in the feed-preparation first stage. In a typical single-stage process, both hydrocracking and denitrogenation occur in the single stage. My improved hydrocracking process is adaptable to either a single-stage system or a multiple-stage hydrocracking system. The feed-preparation treatment may be operated in the liquid phase, the vapor phase, or mixed vapor-liquid phase. The catalyst may be of a fixed-bed type, a staged fluidized-bed type, or some other appropriate type of system. Feedstocks which may be used may be derived from petroleum, shale, gilsonite, and other sources.

Those petroleum hydrocarbon feedstocks which may be hydrocracked satisfactorily in my improved process may have a wide range of compositions. Such feedstocks may consist essentially of all saturates, or they 'may consist of practically all aromatics, or they may be mixtures of the two types of hydrocarbons. The saturates are hydrocracked to gasolineboiling-range parafiins containing isoparaffms in the product in a concentration that is greater than that found for equilibrium. The polynuclear aromatics are partially hydrogenated and the hydrogenated ring portion is hydrocracked to produce a partially substituted benzene and isoparaffin. Suitable feedstocks may contain the high-boiling fractions of crude oil, which may boil at a temperature as high as l,200 F. However, generally the feedstock will range from naphtha and kerosene to and through the heavy gas oils. Normally the feedstocks will boil between 350 F. and about 850 F. Therefore, a light catalytic cycle oil, which boils in the range of 350 to 650 F., a heavy catalytic cycle oil which boils in the range of about 500 F. to about 800 E, and a virgin gas oil which boils in the range of about 400 F. to about l000F. are suitable feedstocks.

Amounts of sulfur which are found in such feedstocks do not generally affect adversely the catalyst employed in the hydrocracking stage. However, as noted above, combined nitrogen, as well as oxygen, in such feedstocks, deleteriously affect the hydrocracking catalyst; therefore, their concentration in the feedstocks should be maintained as low as possible in order to provide the desired rate of reaction in the hydrocracking zone without accelerating hydrocrackingcatalyst contamination and deactivation. Such feedstock, as mentioned above, may contain as much as 0.1 weight percent nitrogen, or even higher. This nitrogen concentration is readily reduced in the feed-pretreatment zone to a value which is conducive to a more satisfactory catalyst life.

In an embodiment of my improved hydrocracking process, as is done in many of the conventional two-stage hydrocracking processes, the petroleum hydrocarbon feedstock is contacted with a suitable hydrofining catalyst in the presence of hydrogen in the feed-preparation zone. Elevated temperatures and pressures are employed. Suitable hydrofining catalysts include those which comprise the oxides and/or sulfides of the Group Vl-B and/or Group VIII metals supported on a suitable carrier. Examples of satisfactory carriers are alumina, titania, and silica-alumina. A cobalt-molybdenum catalyst, supported on a silica-alumina carrier, would be a satisfactory catalyst for use in the feed-preparation zone.

Suitable operating conditions that may be used in the feedpreparation zone include a reactor temperature in the range of about 500 F. to about 800 F., a pressure in the range of about 200 to about 2,500 psig, a hydrogen-to-oil ratio in the range of about 500 standard cubic feet of hydrogen per barrel of hydrocarbon to about 10,000 standard cubic feet of hydrogen per barrel of hydrocarbon, and a liquid hourly space velocity in the range of about 0.2 to about 20. Preferably, the temperature may range from about 600 F to 725 F.; the pressure, from about 1,200 to 1,800 psig; the hydrogen-to-oil ratio, from about 1,000 to about 7,500 standard cubic feet of hydrogen per barrel of hydrocarbon; and the liquid hourly space velocity, from about 0.5 to about 10.0 volumes of hydrocarbon per hour per volume of catalyst.

In the hydrocracking zone, the hydrocarbons are contacted with a suitable hydrocracking catalyst in the presence of hydrogen at elevated temperatures and pressures. Such catalysts may be selected from various well-known hydrocracking catalysts, which typically comprise a hydrogenation component and a solid acidic cracking component.

The hydrogenation component possesses hydrogenationdehydrogenation activity and may exist in the metallic form or as a compound such as the oxides or sulfides thereof. A large number of well-known metallic hydrogenation catalysts may be used in the hydrocracking catalyst. Preferably, this metallic hydrogenation catalyst is selected from the metals of Group VIII of the Periodic Table, for example, cobalt, nickel, and platinum, or from the metals of Group VIB,. for example, molybdenum and tungsten. These hydrogenation components can be introduced into the catalyst by impregnating the acidic cracking component with a heat-decomposible compound of the hydrogenation metal and then calcining the resulting composite.

The acidic cracking component of the hydrocracking catalyst may be made up of one or more of the following solid acidic components: Silica-alumina (naturally occurring and/or synthetic), silica-alumina-zirconia, silica-magnesia, acidtreated-aluminas, with or without halogens, such as fluorided alumina, boria alumina, and the various heteropoly acidtreated-aluminas, and other similar solid acidic components. Each acidic component must possess substantial cracking activity in the finished catalyst composite. The preparation and the properties of such acidic cracking components are well known to those skilled in the art and need not be considered further. A discussion of these components may be found in Emmetts Catalysis, Volume 7, Reinhold Publishing Corporation, Pages 1-9 1.

The preferred hydrocracking catalyst also comprises an activity-control-affording material. Such a material balances the activities of the various catalytic elements so that a low rate for hydrogenation relative to that for isomerization results. Such balanced activities in the catalyst provide more branched paraffins and a better product distribution. The normally solid elements of the Group Vl-A of the Periodic Table, particularly sulfur, and the normally solid elements of Group V-A of the Periodic Table, particularly arsenic and antimony, and metals such as lead, mercury, copper, zinc, and cadmium can provide an advantageous balance in activities between the metallic hydrogenation component and the solid acidic component. Such activity-control-affording elements may be introduced into the catalyst during the catalyst manufacture by impregnating a composite of a hydrogenation component on a solid acidic component with a solution of an organic or inorganic compound, for example, triphenyl arsine, mercuric nitrate, and arsenic trioxide. Of course, the composite of hydrogenation component on acidic cracking component could be treated with a sulfur compound, such as hydrogen sulfide or carbon disulfide. Only small amounts of these activity-control-affording elements are required in the catalyst. Therefore, in the case of arsenic or antimony, only about 0.1 to 5 moles of arsenic or antimony, preferably about 0.1 to 1 mole, and optimally about 0.25 to 0.75 mole, of these elements are used per mole of the hydrogenation metal. Not only will the use of these activity-control-afiording elements result in an increase of branched-chain paraffms, but also catalyst regeneration is facilitated.

Suitable operating conditions that are employed in the hydrocracking zone include a temperature from about 450 F. to about 750 F., a pressure from about 200 to 2,500 psig, a liquid hourly space velocity from about 0.2 to about 5 volumes of hydrocarbon per hour per volume of catalyst, and a hydrogen-to-oil ratio from about 2,000 to about 15,000 standard cubic feet of hydrogen per barrel of hydrocarbon. Preferably, the temperature is from 500 F. to 700 F.; the pressure, from about 1,200 to about 1,800 psig; the liquid hourly space velocity from about 0.5 to about 2 volumes of hydrocarbon per hour per volume of catalyst; and the hydrogen-to-oil ratio, from about 5,000 to about 10,000 standard cubic feet of hydrogen per barrel of hydrocarbon.

The following Example I is presented for the purpose of illustration only and is not intended to limit my invention. This example depicts a preferred embodiment of my improved hydrocracking process.

EXAMPLE I Referring to the accompanying FIG. 1, a light gas oil feedstock is introduced into the hydrocracking system via line 11. This hydrocarbon feed contains more than 20 parts per million of nitrogen and is preheated prior to its passage through line 11. Approximately 15,000 barrels of hydrocarbon are used per day. This preheated feed passes through line 11 and line 12 into reaction zone 13. The reaction zone 13 may be broken down into a hydrocracking zone 14 and a hydrodenitrogenation or feed-preparation zone 15. The hydrocracking zone 14 is located upstream from the feedpreparation zone 15. Line 12 joins the reaction zone 13 at the interface between hydrocracking zone 14 and feed-preparation zone 15.

The hydrocracking zone 14 comprises four individual beds of hydrocracking catalyst. These four catalyst beds are numbered consecutively 1 through 4 with bed 1 being the initial bed in hydrocracking zone 14 and bed 4 being the terminal bed of hydrocracking zone 14.

The feed-preparation zone 15 comprises two individual beds of hydrodenitrogenation catalyst. These two beds are numbered consecutively 5 and 6, bed 5 being the initial bed in the feed-preparation zone 15 and bed 6 being the terminal bed in feed-preparation zone 15.

Advantageously, the nitrogen-compound-containing feedstock enters the reaction zone 13 and commingles with the hydrocrackate, i.e., the effluent from the hydrocracking zone 14. The mixed feed-hydrocrackate stream is passed into the feed-preparation zone 15 and through the catalyst beds therein. The two beds contain nickel-tungsten-sulfide-on-silica-alumina catalyst. A liquid hourly space velocity within the range of 3 to 5 volumes of hydrocarbon per hour per volume of catalyst is maintained in feed-preparation zone 15. Initially, the temperature at the top of catalyst bed 5 is 700 F. and the temperature at its bottom is 720 F. Approximately million standard cubic feet of cold hydrogen per day are introduced into feed-preparation zone between beds 5 and 6 to provide cooling therein. The top of bed 6 initially has a temperature of about 700 F. and its bottom a temperature of about 720 F. As the run progresses, the feed-preparation catalyst ages and deactivates. As this deactivation occurs, less cold hydrogen is injected through line 16 so that by the time the run is terminated, little or no cool hydrogen is being injected into the system between beds 5 and 6. The final temperatures of these two catalyst beds are: at the top of bed 5, 730 F at the bottom of bed 5, 750 F.; at the top of bed 6, 750 F.; and at the bottom of bed 6, 770 F.

The effluent from feed-preparation zone 15 is passed through line 17, condenser 18, and line 19 into flash drum 20, where a temperature of 550 F. exists at a pressure of approximately 1,400 psia. In flash drum 20, the heavier material, principally gas oil, is separated from the flashed material, which is removed from flash drum 20 through line 21 into and through condenser 22 and line 23 into liquid-gas separator 24. Approximately 18,400 barrels of the heavy material per day are separated from the flashed material in flash drum 20. This heavier material is made'up essentially of 83 percent gas oil and 17 percent gasoline, and it is removed from flash drum 20 through line 25.

In liquid-gas separator 24, the light gases containing hydrogen are separated from the cool effluent which is introduced into separator 24. The temperature in liquid-gas separator 24 is about 100 F.; and the pressure, about 1,390 psia. The light gases are removed from separator 24 through line 26. Make-up hydrogen is added to this light gas via line I 27. This make-up hydrogen stream contains approximately 85 percent hydrogen by volume and is added to the stream at a rate of about 40 million standard cubic feet of gas per day. This make-up hydrogen gas is mixed with the light-gas stream in line 26, and the mixed hydrogen-containing-gas stream is passed through line 28, compressor 29, and line 30, to be recycled to reaction zone 13. The mixed hydrogen-containing-gas stream now contains approximately 80 percent hydrogen by volume and is returned to reaction zone 13 at a rate of about 210 million standard cubic feet of gas per day.

The liquid from liquid-gas separator 24 is passed through line 31 into fractionator 32, where material boiling in the gasoline-boiling range and/or distillates are separated therefrom and removed from the system as products by way of lines 33, 34, and 35. These products would include 850 barrels of propane per day, 2,600 barrels of butane per day, and 15,700 barrels of material boiling in the gasoline-boiling range per day. The heavier material which is withdrawn from fractionator 32 and which is hereinafter called the hydrocracking feed, is passed through line 36, pump 37, lines 38, 39, 40, and 41 into heater 42. The heavier material removed from flash drum 20 via line 25, as discussed above, is added to the hydrocracking feed in line 39 by way of pump 25a and line 25b and becomes a part of the hydrocracking feed.

A major portion of the hydrogen-containing-gas stream from line 30 is passed through lines 43 and 44 to join and be commingled with the recycled hydrocracking feed. The commingled gas-hydrocracking-feed stream is passed through line 41, heater 42, and line 45 into the top of hydrocracking zone 14. In addition, the rest of the hydrogen-containing-gas stream, approximately 10 million cubic feet of this gas per day, is passed from line 30 through line 46 into line 16, from which it is introduced cold into the feed-pretreatment zone 15, as explained above.

The heated, commingled hydrogen-containing-gashydrocracking-feed stream is passed down through the catalyst beds 1 through 4 in hydrocracking zone 14. Preheated hydrocarbon feed containing nitrogen is passed through lines 47 and 48 from line 11 into hydrocracking zone 14 between catalyst bed 1 and catalyst bed 2. Hydrocarbon feed is passed also through line 49 from line 47 into hydrocracking zone 14 between catalyst bed 2 and catalyst bed 3 and through line 50 from line 47 into hydrocracking zone 14 between catalyst bed 3 and catalyst bed 4. As pointed out above, this hydrocarbon feedstock contains at least 20 parts per million nitrogen, which is used as a selective poison to temporarily poison the hydrocracking catalyst in the hydrocracking zone 14 so as to control the rate of hydrocracking reaction, even though increased catalyst temperatures are employed. Therefore, sufficient hydrocarbon feed is added to the hydrocracking zone 14 via lines 48, 49 and 50 to effectively control the rate of the hydrocracking reaction.

Initially, the temperatures in the hydrocracking zone are as follows: at the top of bed 1, 580 F.; at the bottom of bed 1 and the top of bed 2, 610 F at the bottom of bed 2 and at the top of bed 3, 640 F.; at the bottom of bed 3 and at the top of bed 4, 670 F.; and at the bottom of bed 4, 700 F. As the run progresses, the catalyst deactivates and less nitrogen-containing compounds need be used to poison the catalyst to hold the temperature differential across the catalyst beds at the desired level. In this way, increased temperatures can be used throughout the hydrocracking zone. At the termination of the run, the following temperatures are found: at the top of catalyst bed 1, 610 F.; at the bottom of bed 1 and the top of bed 2, 640 F.; at the bottom of bed 2 and the top of bed 3, 670 F.; at the bottom of bed 3 and the top of bed 4, 700 F.; and at the bottom of bed 4, 730 F.

The catalyst in each of these beds, that is, beds 1 through 4, is a hydrocracking catalyst comprising arsenided nickel on a fluorided silica-alumina support. The catalyst contains 4.5 percent nickel, 2.3 percent arsenic, and 2.9 percent fluorine on a silica-alumina cracking catalyst. A liquid hourly space velocity in the hydrocracking zone 14 is maintained at approximately 15 volumes of hydrocarbon per hour per volume of catalyst. The pressure in the reaction zone 13, including hydrocracking zone 14 and feed-pretreatment zone 15, is about 1,400 psia.

This improved hydrocracking system not only uses only one stream of make-up hydrogen-containing gas and one stream of recycled hydrogen-containing gas, but also may be operated at relatively high temperatures with the use of a minimum amount of heat-exchange equipment without causing rapid deactivation of the hydrocracking catalyst. The temperature is allowed to increase substantially in the upper part of reaction zone 13. Furthermore, the partially condensed effluent from reaction zone 13 is flashed to separate out the heavy liquid, which is recycled back to the reaction zone 13 without further cooling. These operations effectively minimize the amount of heat-exchange surface needed. Less fuel and less cooling water are required as a result. The reduction in gas streams, which results in a minimum amount of gas-compressing equipment being needed, and the reduced amount of heat-exchange surface, fuel and cooling water, offer economic advantages to those who use this specific embodiment of my improved hydrocracking process. Reduced investment and operating costs are achieved.

EXAMPLE ll Example ll is presented for comparative purposes and considers the operation of a hydrocracking process employing techniques that are well known to those skilled in the art, that is, a hydrocracking process of standard or conventional design. Both recycle hydrogen and pretreated feed are employed for quench purposes.

A simplified schematic flow diagram of this standard or conventional hydrocracking operation is presented in FIG. 2.

Referring to FIG. 2, light gas oil feedstock that is employed in Examplel is introduced into the hydrocracking system via Line 51. As is done in Example I, this hydrocarbon feedstock, which contains more than 20 parts per million of nitrogen, is preheated to a temperature of 500 F. prior to its passage through line 51. Approximately 15,000 barrels of this hydrocarbon feedstock are charged to the unit per day. This preheated feedstock passes through Line- 51 into reaction zone 52. The reaction zone 52 comprises a hydrocracking zone 53 and a hydrodenitrogenation zone or feed-preparation zone 54. The hydrocracking zone 53 is located upstream from the feed-preparation zone 54. Line 51 joins the reaction zone 52 at the interface between hydrocracking zone 53 and feed preparation zone 54.

The hydrocracking zone 53 comprises four individual beds of hydrocracking catalyst. These four catalyst beds are numbered consecutively 55 through 58, with bed 55 being the initial bed in hydrocracking zone 53 and bed 58 being the terminal bed in hydrocracking zone 53. The hydrocracking catalyst in each of these catalyst beds 55 through 58 is the same as the hydrocracking catalyst that is employed in Example I.

The feed-preparation zone 54 comprises two individual beds of hydrodenitrogenation catalyst. These two beds are numbered consecutively 59 and 60, bed 59 being the initial bed in the feed-preparation zone 54 and bed 60 being the terminal bed in the feed-preparation zone 54. As in the process of the invention which is described in Example I, the nitrogencompound-containing feedstock enters the reaction zone 52 and commingles with the hydrocrackate from hydrocracking zone 53. The mixed feed-hydrocrackate stream is passed into the feed-preparation zone 54 and through the two catalyst beds therein. The catalyst employed in these two beds is the same as that employed in the feed-preparation zone in Example i, that is, nickel-tungsten-sulfide-on-silica-alumina catalyst. As in Example I, a liquid hourly space velocity within the range of about 3 to 5 volumes of hydrocarbon per hour per volume of catalyst is employed in the feed-preparation zone 54. initially, the temperature at the top of catalyst bed 59 is 700 F. and the temperature at its bottom is about 720 F. Approximately l million standard cubic feet of cold hydrogen per day are introduced into the feed-preparation zone 54 at the interface between catalyst beds 59 and 60 by way of line 96. The temperature at the top of bed 60 is initially about 700 F. and the temperature at its bottom is about 720 F.

During the course of the run, the feed-preparation-zone catalyst ages and deactivates, with an accompanying reduced requirement of cold hydrogen. The final temperatures at the top and bottom of bed 59 are 750 F. and 770 F respectively. These latter two temperatures are also the final temperatures at the top and bottom of catalyst bed 60.

The effluent from feed-preparation zone 54 passes through line 61, condenser 62, and line 63 into flash drum 64, where a temperature of about 550 F. and a pressure of approximately 1,400 psia are maintained. In flash drum 64, the heavier hydrocarbons are separated from the flashed material, which is removed from flash drum 64 through line 65. The flashed material is passed through condenser 66 and line 67 into liquid-gas separator 68.

in liquid-gas separator 68, the light gases containing hydrogen are separated from the cooled material which is introduced into the separator 68. The temperature in liquid-gas separator 68 is about 100 F.; and the pressure, about 1,390 psia. The light gases are removed from separator 68 through line 69. If necessary, make-up hydrogen is added to these light gases via line 70. The make-up hydrogen and light gas streams are mixed and the resulting hydrogen-containing gas stream is passed through line 71, compressor 72, and line 73 to be recycled to reaction zone 52.

The liquid product from separator 68 is passed through line 74 into fractionator 75, where material boiling in the gasoline boiling range and/or distillates are separated therefrom and removed from the system as usable products by way of lines 76, 77, and 78. The heavier material which is withdrawn from fractionator 75, the hydrocracking feed, is passed through line 79, pump and lines 81, 82, and 83. The hydrocracking feed is then commingled with hydrogen-containing gas and passed through line 84, heater 85, and line 86, into the top of reaction zone 52. The heavier material removed from flash drum 64 is passed by way of line 87 and pump 88 into line 89. A major portion of this heavier material is introduced into line 82, where it is admixed with and becomes a part of the hydrocracking feed. A minor portion of the heavier material from flash drum 64 that is passing through line 89 is directed by way of line 97, cooler 98, and line 99 to be used as quench medium in hydrocracking zone 53, as discussed hereinbelow.

The cooled hydrocarbons in Line 99 are introduced into lines 100 and 101. The cooled hydrocarbons in line 100 are added to and commingled with the hydrogen-containing gas in line to be introduced into hydrocracking zone 53 between catalyst beds 57 and 58. The cooled hydrocarbon stream in line 101 is divided into two hydrocarbon streams passing through lines 102 and 103. The cooled hydrocarbons in line 102 are added to and commingled with the hydrogen-containing gas in line 94 to be introduced into hydrocracking zone 53 between catalyst beds 56 and 57. The cooled hydrocarbon stream in line 103 is added to and commingled with the hydrogen-containing gas in line 93 to be introduced into hydrocracking zone 53 between catalyst beds 55 and 56. Therefore, in this conventional operation, quenching of the hydrocracking zone 53 is obtained by the introduction of streams of mixed hydrogen-containing gas and cooled pretreated hydrocarbons into the hydrocracking zone between the catalyst beds in that zone.

Initially, the temperatures in the hydrocracking zone 53 are as follows: 580 F. at the top of each of the catalyst beds 55, 56, 57, and 58; 610 F. at the bottom of each of these beds. During the course of the run, the catalyst deactivates and temperatures are increased to compensate for such deactivation. At the termination of the run, the following temperatures are found: 700 F. at the top of each of the catalyst beds55, 56, 57 and 58; 730 F. at the bottom of these beds. The liquid hourly space velocity and pressure in hydrocracking zone 53 are the same as those employed in hydrocracking zone 14 in Example 1.

Flow rates for various hydrogen streams and hydrocarbon streams are presented in Table l hereinbelow.

TABLE I.FLOW RATES TO HYDROCRACKING ZONE Flow rates, barrels/day Conventional Invention design design Pretreated feed Initial Final Initial Final Feed inlet (line 86 or 45) 18, 900 19, 650 23, 23, 100 ,To first quench (line 93) 1, 300 1, 100 To second quench (line 94) 1, 400 1,

1T0 third quench (line 95) 1, 500 1, 200

Flow rates, million cubic feet/day Second quench (line 94) 12. 3 Third quench (line 95) 1 Calculations to estimate the heat duties that are required to either heat or cool the pretreated and raw hydrocarbon streams have been made. The results of these calculations are presented in Table II which compares the heat duties and design duties of the standard or conventional design, as described in Example II, to those heat and design duties of the process of the present invention, as described in Example I. In both cases, the raw hydrocarbon feed was introduced into the reaction zone at an assumed temperature of 500 F.

TABLE II.HEAT AND DESIGN DUTIES Heat duties, million B.t.u./hr.

In both Table I and Table II, the term Conventional Design refers to the design associated with the embodiment of the conventional or standard hydrocracking process that is depicted in Example 11. The term Invention Design is directed to the design of the hydrocracking process which is presented hereinabove in Example I as an embodiment of the process of the present invention.

The data presented in Table 11 clearly show that the heat duties of the standard or conventional design process are much greater than those employed with the improved process of the present invention. With the present invention, the investment cost is reduced. Moreover, the operating cost is significantly reduced, since additional heat need not either be added to nor removed from the system during operation.

The data in Table II point out that the amount of external heat being used in the process of the present invention is substantially less than that of conventional hydrocracking operation. This reduction in external heat results from substitution therefor of the heat that results from the controlled increase in the rate of reaction that is occurring in the hydrocracking zone.

The embodiment of the process of the present invention in Example I is a preferred embodiment and, as pointed out above, is presented for the purpose of illustration only and is not intended to limit the scope of the invention. In another embodiment of my improved hydrocracking process, the cooling of the feed-preparation zone may be accomplished by introducing, in place of cool hydrogen-containing gas, a portion of the heavier material obtained from the flash drum into the feed-preparation zone between the catalyst beds in that zone. In still another embodiment, a catalyst having both hydrodenitrogenation activity and hydrocracking activity may be employed in the feed-preparation zone.

What is claimed is:

1. A process for hydrocracking a petroleum hydrocarbon feedstock containing at least 20 parts per million of nitrogen, which process comprises: introducing into a feed-preparation zone said feedstock to reduce the amount of nitrogen in said feedstock; contacting said feedstock with a hydrofining catalyst under hydrofining conditions in said feed-preparation zone to provide treated feedstock; supplying external heat to at least part of the treated feedstock to provide heated treated feedstock; introducing the heated treated feedstock into a hydrocracking zone to contact a hydrocracking catalyst under hydrocracking conditions; introducing additional feedstock containing at least 20 parts per million of nitrogen into said hydrocracking zone at a plurality of points spaced along the length of said hydrocracking zone to provide an increasing amount of nitrogen along the length of said hydrocracking zone in the direction of flow through said hydrocracking zone, said increasing amount of nitrogen being effective to control the rate of reaction in said hydrocracking zone so that the heat of the hydrocracking reaction may be used effectively to reduce external heat supplied to the hydrocarbons prior to their entry into said hydrocracking zone, without appreciably deactivating the hydrocracking catalyst, said external heat being reduced by the substitution therefor of the heat resulting from the controlled increase in the rate of reaction occurring in said hydrocracking zone; and recovering the lower-boiling hydrocarbons as usable petroleum products.

2. The process of claim 1 wherein said feedstock and said additional feedstock are derived from the same supply of feedstock to be treated by said process.

3. The process of claim 1 wherein said petroleum hydrocarbon feedstock is a light catalytic cycle oil which boils within the range of about 350F. to about 650F. and contains at least 20 parts per million of nitrogen.

4. The process of claim 1 wherein said petroleum hydrocarbon feedstock is a heavy catalytic cycle oil which boils within the range of about 500F. to about 800F. and contains at least 20 parts per million of nitrogen.

5. The process of claim 1 wherein said petroleum hydrocarbon feedstock is a virgin gas oil which boils within the range from about 400F. to about l,00OF. and contains at least 20 parts per million of nitrogen.

6. The process of claim 1 wherein said hydrofining catalyst has hydrocracking activity.

7. A process for hydrocracking a petroleum hydrocarbon feedstock containing at least 20 parts per million of nitrogen, which process comprises: introducing into a feed-preparation zone a mixture of said feedstock and the effluent from a hydrocracking zone, as hereinafter defined, to contact a hydrofining catalyst under hydrofining conditions; partially cooling the effluent from said feed-preparation zone; flashing the partially cooled efiluent from said feed-preparation zone to remove a heavy bottoms fraction; cooling the flashed material; separating hydrogen-containing light gases from the cooled flashed material; adding make-up-hydrogen-containing light gas to said separated hydrogen-containing light gases to form a combined-hydrogen-containing gas stream; passing to a hydrocracking zone said combined-hydrogen-containing gas stream; fractionating in a fractionation zone the remainder of said flashed material to separate light overhead products and a heavier-liquid effluent; passing to said hydrocracking zone said heavier liquid effluent and at least a first portion of said heavy bottoms fraction; commingling said heavier liquid effluent and said first portion of said heavy bottoms fraction with said combined-hydrogen-containing gas stream to obtain a mixed hydrogen-hydrocarbon stream; supplying external heat to the mixed hydrogen-hydrocarbon stream; introducing into said hydrocracking zone the heated mixed hydrogenhydrocarbon stream; hydrocracking in said hydrocracking zone said heated mixed hydrogen-hydrocarbon stream in the presence of a hydrocracking catalyst under hydrocracking conditions; introducing additional feedstock containing at least 20 parts per million of nitrogen into said hydrocracking zone at a plurality of points spaced along the length of said hydrocracking zone to provide an increasing amount of nitrogen along the length of said hydrocracking zone in the direction of flow through said hydrocracking zone, said increasing amount of nitrogen being effective to control the rate of reaction in said hydrocracking zone so that the heat of the hydrocracking reaction may be used effectively to reduce external heat supplied to the hydrocarbons prior to their entry into said hydrocracking zone, without appreciably deactivating the hydrocracking catalyst, said external heat being reduced by the substitution therefor of the heat resulting from the controlled increase in the rate of reaction occurring in said hydrocracking zone; mixing said eflluent from said hydrocracking zone with said feedstock, as noted hereinbefore, prior to introducing said mixture into said feed-preparation zone; and recovering said light overhead products as usable hydrocarbon products.

8. The process of claim 7 wherein said hydrocracking catalyst comprises a Group VIII metal hydrogenation component, a solid acidic cracking component and from 0.1 to 1 mol of activity-control-affording element selected from the group consisting of sulfur and the normally solid elements of Group V-A of the Periodic Table per mol of said Group VIII metal to provide a hydrogenation-component activity low in relation to the activity of said acidic cracking component and to provide a gasoline-boiling-range product rich in isoparaffins.

9. The process of claim 7 wherein said hydrocracking catalyst comprises sulfided nickel on a silica-alumina cracking component.

10. The process of claim 7 wherein a second portion of said heavy bottoms fraction is introduced into said feed-preparation zone at at least one point to control the temperature in said feed-preparation zone.

11. The process of claim 7 wherein an amount of said hydrogen-containing light gases is introduced into said feedpreparation zone at at least one point to maintain the desired temperature in said feed-preparation zone.

12. The process of claim 7 wherein said hydrocracking catalyst comprises arsenic and nickel on a silica-alumina cracking component.

13. The process of claim 7 wherein said hydrocracking catalyst comprises arsenic and nickel on a fluorided silica-alumina cracking component.

14. The process of claim 7 wherein said light overhead products comprise hydrocarbons boiling in the gasoline boiling range.

15. The process of claim 7 wherein said light overhead products comprise hydrocarbon distillates.

16. The process of claim 7 wherein said light overhead products comprise hydrocarbon distillates and hydrocarbons boiling in the gasoline boiling range.

17. The process of claim 7 wherein said hydrofining catalyst comprises more than one hydrogenation component, each of which is selected from the group which consists of the elements in Group VI-B and Group VIII of the Periodic Table, and the oxides and sulfides thereof, supported on an adsorbent oxide carrier.

18. The process of claim 7 wherein said hydrofining catalyst comprises nickel-tungsten-sulfide on a silica-alumina cracking component.

19. In a two-stage process for hydrocracking a hydrocarbon feedstock wherein said feedstock is introduced into a feedpreparation zone, said feedstock is treated in said feedpreparation zone in the presence of a hydrofining catalyst under hydrofining conditions, effluent from said feed-preparation zone is flashed to remove a heavy-bottoms fraction, hydrogen-containing light gases are separated from the flashed material, the separated hydrogen-containing light gases are passed to a hydrocracking zone, the remainder of said flashed material is fractionated in a fractionation zone to separate light overhead products and a heavy liquid eflluent, said heavy liquid eflluent is passed to said hydrocracking zone and is commingled with said hydrogen-containing light gases and make-up hydrogen-containing gas to obtain a mixed hydrogen-hydrocarbon stream, said mixed hydrogenhydrocarbon stream is introduced into said hydrocracking zone, and said mixed hydrogen-hydrocarbon stream is hydrocracked in said hydrocracking zone} in the presence of a hydrocracking catalyst under hydrocracking conditions, the improvement which comprises introducing hydrocarbons containing at least 20 parts per million of nitrogen into said hydrocracking zone at a plurality of points spaced along the length of said hydrocracking zone to provide an increasing amount of nitrogen along the len of said hydrocracking zone in the dlrec on of flow throu said hydrocracking zone,

said increasing amount of nitrogen being effective to control the rate of reaction in said hydrocracking zone so that the heat of the hydrocracking reaction may be used effectively to reduce external heat supplied to hydrocarbons prior to their entry into said hydrocracking zone, without appreciably deactivating the hydrocracking catalyst, said external heat being reduced by the substitution therefor of the heat resulting from the controlled increase in the rate of reaction occurring in said hydrocracking zone.

20. A process for hydrocracking a petroleum hydrocarbon feestock containing at least 20 parts per million of nitrogen, which process comprises: hydrofining in a feed-preparation zone said feedstock to reduce the amount of nitrogen in said feedstock and to provide a treated feedstock; supplying external heat to at least part of the treated feedstock to provide heated treated feedstock; introducing the heated treated feedstock into a hydrocracking zone to contact a hydrocracking catalyst under hydrocracking conditions; introducing additional feedstock containing at least 20 parts per million of nitrogen into said hydrocracking zone at one additional point along the length of said hydrocracking zone to provide an increasing amount of nitrogen along the length of said hydrocracking zone in the direction of flow through said hydrocracking zone, said increasing amount of nitrogen being effective to control the rate of reaction in said hydrocracking zone so that the heat of the hydrocracking reaction may be used effectively to reduce external heat supplied to the hydrocarbons prior to their entry in said hydrocracking zone, without appreciably deactivating the hydrocracking catalyst, said external heat being reduced by the substitution therefor of the heat resulting from the controlled increase in the rate of reaction occurring in said hydrocracking zone; and recovering the low-boiling hydrocarbons as usable petroleum products.

. 1972 Patent No. 3,657 Dated April 18,

Robert J. Hengstebeck Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1 line 18, "process" should read processes lines 46 and Z7, "hydrocracking process" should read hydro- Column 2 line 14 "undersired" should read l ific l e ired Column 4, line 23, between "bottom" and "steam" insert the following:

of the zone may in excess of lO0F. the temperature increases, more nitrogen is required to control. the accompanying increased rate of reaction '50 that the hydrogen pressure at the catalyst surface will not be reduced to a level at which rapid catalyst deactivation results The combination of increased temperature and controlled rate of reaction provides a temperature which is sufficiently high to permit the exothermic hydrocracking reaction to furnish sufficient heat so that the amount of heat that must be supplied to the hydrocracking zone by external means can be reduced.

As a result, addition of the selective poison permits a desired temperature to be maintained in the hydrocracking zone, minimizes catalyst de- I activation, and reduces the amount of the external heat that must be supplied to the hydrocracking zone.

FORM PC4050 (10-59) USCOMM-DC 6O376-P69 U.$, GOVERNMENT PRINTING OFFICE: 969 o-'3fi5'334.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,657,110 Dated April 18, 1972 k Pa e 2 lnventofls) Robert J. Hengstebec g g It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Accordingly, an embodiment of my hydrocracking process comprises: introducing a first portion of feedstock containingat least 20 parts per million of nitrogen. into a feed-preparation zone in the presence of a hydrofining catalyst under hydrofining conditions; partially cooling the effluent from the feed-preparation zone; flashing the partially cooled effluent from the feed-preparation zone to remove a hear bottoms fraction; cooling the flashed material; separating hydrogencontaining light gases from the cooled flashed material; adding make-uphydrogen-containing light gas to the separated hydrogen-containing light gases to form a combined hydrogen-containing gas stream; passing to a hydrocracking zone the combined-hydrogen-containing gas stream; fractionating in a fractionation zone the remainder of the flashed material to 1 4/ WA) 1 separate light overhead products and ehem levliquid effluent; passing to the hydrocracking zone the heavier liquid effluent and at least a first FORM PO-10 (10-69) uscoMM-oc 60376-P69 LLS. GOVERNMENT PRINT NG OFFICE: 1969 0-366-334.

U ITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 2 657-, 110 Dated April 18 1972 lnventofls) Robert J. Hengstebeck Page 3 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

portion of the heavier bottoms fraction; comingling the heavier liquid effluent and the first portion of said heavy bottoms fraction with the combined-hydrogen-containing gas stream to obtain a mixed hydrogen-hydro carbon stream; supplying external heat; to the mixed hydrogen-hydrocarbon Signed and sealed this 15th day of August 1972.

(SEAL v Attest:

EDWARD M.PLETCIIER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents FORM PO-105O (10-69) USCOMM-DC 50376-P69 LLS GOVERNMENT PRINTING OFFICE i569 0-366-334, 

2. The process of claim 1 wherein said feedstock and said additional feedstock are derived from the same supply of feedstock to be treated by said process.
 3. The process of claim 1 wherein said petroleum hydrocarbon feedstock is a light catalytic cycle oil which boils within the range of about 350* F. to about 650* F. and contains at least 20 parts per million of nitrogen.
 4. The process of claim 1 wherein said petroleum hydrocarbon feedstock is a heavy catalytic cycle oil which boils within the range of about 500* F. to about 800* F. and contains at least 20 parts per million of nitrogen.
 5. The process of claim 1 wherein said petroleum hydrocarbon feedstock is a virgin gas oil which boils within the range from about 400* F. to about 1,000* F. and contains at least 20 parts per million of nitrogen.
 6. The process of claim 1 wherein said hydrofining catalyst has hydrocracking activity.
 7. A process for hydrocracking a petroleum hydrocarbon feedstock containing at least 20 parts per million of nitrogen, which process comprises: introducing into a feed-preparation zone a mixture of said feedstock and the effluent from a hydrocracking zone, as hereinafter defined, to contact a hydrofining catalyst under hydrofining conditions; partially cooling the effluent from said feed-preparation zone; flashing the partially cooled effluent from said feed-preparation zone to remove a heavy bottoms fraction; cooling the flashed material; separating hydrogen-containing light gases from the cooled flashed material; adding make-up-hydrogen-containing light gas to said separated hydrogen-containing light gases to form a combined-hydrogen-containing gas stream; passing to a hydrocracking zone said combined-hydrogen-containing gas stream; fractionating in a fractionation zone the remainder of said flashed material to separate light overhead products and a heavier-liquid effluent; passing to said hydrocracking zone said heavier liquid effluent and at least a first portion of said heavy bottoms fraction; commingling said heavier liquid effluent and said first portion of said heavy bottoms fraction with said combined-hydrogen-containing gas stream to obtain a mixed hydrogen-hydrocarbon stream; supplying external heat to the mixed hydrogen-hydrocarbon stream; introducing into said hydrocracking zone the heated mixed hydrogen-hydrocarbon stream; hydrocracking in said hydrocracking zone said heated mixed hydrogen-hydrocarbon stream in the presence of a hydrocracking catalyst under hydrocracking conditions; introducing additional feedstock containing at least 20 parts per million of nitrogen into said hydrocracking zone at a plurality of points spaced along the length of said hydrocracking zone to provide an increasing amount of nitrogen along the length of said hydrocracking zone in the direction of flow through said hydrocracking zone, said increasing amount of nitrogen being effective to control the rate of reaction in said hydrocracking zone so that the heat of the hydrocracking reaction may be used effectively to reduce external heat supplied to the hydrocarbons prior to their entry into said hydrocracking zone, without appreciably deactivating the hydrocracking catalyst, said external heat being reduced by the substitution therefor of the heat resulting from the controlled increase in the rate of reaction occurring in said hydrocracking zone; mixing said effluent from said hydrocracking zone with said feedstock, as noted hereinbefore, prior to introducing said mixture into said feed-preparation zone; and recovering said light overhead products as usable hydrocarbon products.
 8. The process of claim 7 wherein said hydrocracking catalyst comprises a Group VIII metal hydrogenation component, a solid acidic cracking component and from 0.1 to 1 mol of activity-control-affording element selected from the group consisting of sulfur and the normally solid elements of Group V-A of the Periodic Table per mol of said Group VIII metal to provide a hydrogenation-component activity low in relation to the activity of said acidic cracking component and to provide a gasoline-boiling-range product rich in isoparaffins.
 9. The process of claim 7 wherein said hydrocracking catalyst comprises sulfided nickel on a silica-alumina cracking component.
 10. The process of claim 7 wherein a second portion of said heavy bottoms fraction is introduced into said feed-preparation zone at at leaSt one point to control the temperature in said feed-preparation zone.
 11. The process of claim 7 wherein an amount of said hydrogen-containing light gases is introduced into said feed-preparation zone at at least one point to maintain the desired temperature in said feed-preparation zone.
 12. The process of claim 7 wherein said hydrocracking catalyst comprises arsenic and nickel on a silica-alumina cracking component.
 13. The process of claim 7 wherein said hydrocracking catalyst comprises arsenic and nickel on a fluorided silica-alumina cracking component.
 14. The process of claim 7 wherein said light overhead products comprise hydrocarbons boiling in the gasoline boiling range.
 15. The process of claim 7 wherein said light overhead products comprise hydrocarbon distillates.
 16. The process of claim 7 wherein said light overhead products comprise hydrocarbon distillates and hydrocarbons boiling in the gasoline boiling range.
 17. The process of claim 7 wherein said hydrofining catalyst comprises more than one hydrogenation component, each of which is selected from the group which consists of the elements in Group VI-B and Group VIII of the Periodic Table, and the oxides and sulfides thereof, supported on an adsorbent oxide carrier.
 18. The process of claim 7 wherein said hydrofining catalyst comprises nickel-tungsten-sulfide on a silica-alumina cracking component.
 19. In a two-stage process for hydrocracking a hydrocarbon feedstock wherein said feedstock is introduced into a feed-preparation zone, said feedstock is treated in said feed-preparation zone in the presence of a hydrofining catalyst under hydrofining conditions, effluent from said feed-preparation zone is flashed to remove a heavy-bottoms fraction, hydrogen-containing light gases are separated from the flashed material, the separated hydrogen-containing light gases are passed to a hydrocracking zone, the remainder of said flashed material is fractionated in a fractionation zone to separate light overhead products and a heavy liquid effluent, said heavy liquid effluent is passed to said hydrocracking zone and is commingled with said hydrogen-containing light gases and make-up hydrogen-containing gas to obtain a mixed hydrogen-hydrocarbon stream, said mixed hydrogen-hydrocarbon stream is introduced into said hydrocracking zone, and said mixed hydrogen-hydrocarbon stream is hydrocracked in said hydrocracking zone in the presence of a hydrocracking catalyst under hydrocracking conditions, the improvement which comprises introducing hydrocarbons containing at least 20 parts per million of nitrogen into said hydrocracking zone at a plurality of points spaced along the length of said hydrocracking zone to provide an increasing amount of nitrogen along the length of said hydrocracking zone in the direction of flow through said hydrocracking zone, said increasing amount of nitrogen being effective to control the rate of reaction in said hydrocracking zone so that the heat of the hydrocracking reaction may be used effectively to reduce external heat supplied to hydrocarbons prior to their entry into said hydrocracking zone, without appreciably deactivating the hydrocracking catalyst, said external heat being reduced by the substitution therefor of the heat resulting from the controlled increase in the rate of reaction occurring in said hydrocracking zone.
 20. A process for hydrocracking a petroleum hydrocarbon feestock containing at least 20 parts per million of nitrogen, which process comprises: hydrofining in a feed-preparation zone said feedstock to reduce the amount of nitrogen in said feedstock and to provide a treated feedstock; supplying external heat to at least part of the treated feedstock to provide heated treated feedstock; introducing the heated treated feedstock into a hydrocracking zone to contact a hydrocracking catalyst under hydrocracking conditions; introducing additional feedstock containing at least 20 parts per million of nitrogen into said hydroCracking zone at one additional point along the length of said hydrocracking zone to provide an increasing amount of nitrogen along the length of said hydrocracking zone in the direction of flow through said hydrocracking zone, said increasing amount of nitrogen being effective to control the rate of reaction in said hydrocracking zone so that the heat of the hydrocracking reaction may be used effectively to reduce external heat supplied to the hydrocarbons prior to their entry in said hydrocracking zone, without appreciably deactivating the hydrocracking catalyst, said external heat being reduced by the substitution therefor of the heat resulting from the controlled increase in the rate of reaction occurring in said hydrocracking zone; and recovering the low-boiling hydrocarbons as usable petroleum products. 